One hundred and six grams (1 mole) of benzaldehyde(Note 1) and 107 g. (1 mole) of m-toluidine are mixed in a suitable flask; the temperature rises to about 60° (Note 2) and (Note 3). The mixture is cooled below 35° in cold water, 200 ml. of ether is added, and the solution is placed in the steel reaction vessel of a high-pressure hydrogenation apparatus. Eight to ten grams of Raney nickel catalyst (p. 181) is added, the bomb is closed, and hydrogen is admitted up to 1000 lb. pressure (Note 4). The bomb is shaken continuously at room temperature for 15 minutes (Note 5). The contents are removed, and the bomb is washed out with two 200-ml. portions of ether. After the catalyst has been separated by filtration (Note 6), the ether is removed by distillation and the product is distilled from a modified Claisen flask(Note 7). After a small fore-run the N-benzyl-m-toluidine boils at 153–157° /4 mm.; 315–317° /760 mm. The yield is 175–185 g. (89–94%) (Note 8) and (Note 9).

3.
The ether used as solvent may be replaced by an equal amount of 95% ethanol. If ethanol is used, cooling is unnecessary.

4.
The initial pressure of hydrogen used is determined by the apparatus available. The drop in pressure depends upon the size of the bomb.

5.
With a less active Raney nickel catalyst it may be necessary to carry out the reduction at a somewhat higher temperature. If necessary, the reaction mixture may be heated slowly to 60° and the reduction carried out at this temperature. The yield is then somewhat lower (82–84%).

6.
The catalyst is filtered through paper on a Büchner funnel. Owing to its activity, suction should be discontinued as soon as all the liquid has passed through. If this precaution is not observed, a fire may result.

7.
In some instances (o-tolylbenzylamine), a part of the product may crystallize and can be filtered.

8.
The hydrochloride, m.p. 198–199°, may serve for characterization.

9.
According to the submitters, other aromatic aldehydes and amines may be used in a similar manner with essentially the same yield of product. The exact procedure for isolation of the amine will depend upon its physical properties. Benzaldehyde and o-toluidine yield o-tolylbenzylamine, m.p. 56–57° (hydrochloride, m.p. 165–166°), while p-tolylbenzylamine, obtained from p-toluidine, has a b.p. 162–163°/5 mm. (hydrochloride, m.p. 181–182°).

3. Discussion

N-Benzyl-m-toluidine has been prepared by the electrolytic reduction of benzal-m-toluidine,1 and by hydrolysis of N-benzyl-N-formyl-m-toluidine, which was prepared in turn by the reaction of sodium N-formyl-m-toluidine with benzyl chloride.2

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